The Janpan customer order 40GP alumina magnesia carbon bricks.
In order to explore the feasibility of using corundum-spinel castable to replace alumina-magnesia carbon bricks in the bottom working layer of electric furnace ladle, the composition and microstructure of the used castable were analyzed to study its damage mechanism. The results show that the corundum-spinel castable has excellent slag resistance and spalling resistance, small melting loss, long service life, and high safety, and can meet the smelting process of the electric furnace round billet production line; its damage is mainly caused by slag and Caused by the reaction of refractory materials, thermal stress and mechanical stress also play an important role.
Performance comparison of corundum-spinel castables and alumina-magnesia carbon bricks
Corundum-spinel castables are widely used in the working layer below the converter ladle slag line due to their good resistance to alkaline slag erosion and excellent high-temperature mechanical properties. Pre-synthesized or in-situ generated magnesia-aluminum spinel is introduced into corundum castables mainly to improve slag resistance and high-temperature mechanical properties. Pre-synthesized magnesia-aluminum spinel has larger grain size, good chemical stability and low solubility, as well as excellent volume stability, and is especially suitable for use at the bottom of high-temperature and high-pressure ladles.
Compared with alumina-magnesia carbon bricks, corundum-spinel castables do not contain carbon, have a higher volume density, have comparable normal temperature compressive strength and high temperature flexural strength. They expand slightly after burning and show good volume stability. It is inferred from the performance indicators that the corundum-spinel castable can meet the smelting process requirements of the electric furnace round billet production line.
From a performance comparison point of view, the ladle bottom uses corundum-spinel castable instead of alumina-magnesia carbon bricks, which can meet the smelting process of the electric furnace round billet production line. Using integral castables, the melting loss rate of the bottom working layer of the ladle is small, the integrity and air tightness are enhanced, and the probability of cold steel seeping along the brick joints and being offline due to abnormalities in the breathable bricks is significantly improved, and the safety of the ladle operation is significantly improved and optimized. The maintenance mode is changed and the consumption of refractory materials is reduced.
The main differences between cast cladding and brick cladding
1) The turnaround time of the cast bottom is about 24 to 38 hours, with the construction time of 2 hours, the curing time of 16 hours, and the baking time of 36 hours; the construction time of the brick bottom is 4 hours, and the baking time is 12 to 24 hours.
2) The maintenance mode is adjusted. When the brick ladle is repaired, all the working linings at the bottom of the ladle need to be replaced, including the alumina-magnesia carbon bricks at the bottom of the ladle. When repairing the cast ladle, only the breathable bricks, nozzles and impact areas need to be replaced.
Apply the corundum-spinel castable to the bottom working layer of the 150t ladle ladle (13# and 8# ladle) of the Baosteel electric furnace round billet production line, add water 5.0%~5.5% (w), flow value 180~220mm, stir The time is 3 to 5 minutes, and the vibrator is used to vibrate and exhaust, and the total construction time is 1 to 2 hours.
The service life of the two pouring ladle bottoms during overhaul is 92 furnaces and 91 furnaces respectively (normal offline). The remaining thickness of each area during the overhaul of the pouring ladle and brick ladle. There are only minor cracks in the bottom of the cast steel ladle during use. The most severely damaged area during overhaul is in the impact area of the bottom of the ladle, but the residual thickness is >100mm. During the middle repair of the brick cladding, all the working layers of the cladding will be replaced. It can be seen that the corundum-spinel castable can meet the usage conditions of the steel ladle of the electric furnace round billet production line and has a better service life.
The integral casting of the ladle bottom has the following advantages:
1) The number of brick joints in the working layer at the bottom of the ladle is reduced, which reduces the probability of cracking at the bottom of the ladle and the penetration of cold steel along the brick joints, and improves the safety of the use of the ladle.
2) Strengthen the air tightness and integrity of the bottom working layer, reduce the probability of “side blowing” of the breathable bricks, reduce the probability of the breathable bricks being offline due to abnormalities, and improve safety.
3) In the middle and later stages of use, the bricks will not fall off abnormally due to the gradual increase in the brick joints.
4) Mechanical construction is easy to operate and reduces labor intensity.
5) There is no need to replace the entire working layer of the bottom of the package during the intermediate repair. Repair materials are used to protect the impact area of the bottom of the package, which reduces the consumption of refractory materials.